I wouldn't advise "designing" in a 5mil thermal relief or anti-pad. It can be
done, but for a price. For a 1oz copper layer, I design a 8mil thermal/anti
to guarentee 6mils. The fab shop needs some room  to "enhance" the
copper areas, be it the pad or the trace, if you "design" in a 5mil spacing
and your anular ring on your pads is at min., along with a conductor track
at finished size, you leave no room for your vendor to "beef-up" those
areas to guarentee your final requirements. My question to you is, why
so tight? You could also "remove" all unused pads on each layer, this
would give you more relief between signal and ground/pwr. Bottom line,
if you NEED it, do it. It will cost you in lower yeilds, lower yeilds = $$$.
Talk to your vendor.
Dan Lorinser
BFGoodrich Aerospace
Burnsville, MN

>>> Wander, Nicholas G          RV <[log in to unmask]> Jan 29,
1997  7:41 pm >>>

Is a .005 inch gap width (the width of the "no copper" areas) for small   
thermal reliefs a problem? Can this be etched in 1 oz. copper without   
major difficulties?

Nick Wander
Printed Circuit Engineering
Unisys Corp.
Roseville, MN.

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